Wondering why the check engine light is on and what it has to do with code P0456?
Your vehicle has a complex evaporative emissions system to prevent fuel vapors from leaking into your environment. An error code P0456 deals with this system and means there is a small leak detected. Learn more about this essential system and find out how to fix trouble code P0456.
What is the P0456 Error Code?
P0456 is an OBD-II generic code that the engine control module (ECM) has detected a very small leak in the evaporative system during the vehicle off-testing. The test has to fail twice in a row to cause the code to be activated by the ECM.
The evaporative emission control (EVAP) system prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister.
The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned. The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge volume control valve.
The vent control valve is usually open when the engine is at normal operating temperature, and the purge volume control valve is commanded when the ECM is ready to burn the built-up fuel vapors. However, when the vehicle is turned off, the ECM performs a leak test to ensure the evaporative emission control system is working properly.
During the leak test, the ECM closes the vent control valve and purge valve to seal the evaporative system. If the EVAP system does not maintain the pressure, the ECM recognizes an evaporative emission control leak. In the case of P0456, it is a small leak, less than .020” in diameter.
Is P0456 serious?
Don’t worry too much about the P0456 code. It will contribute to air pollution by sending fuel vapours into the atmosphere, and it will activate a check engine light, but it won’t impact the performance of your vehicle immediately. It’s a fairly inexpensive fix as well.
Can I drive with P0456?
Yes, you can drive with a P0456 fault code, but you may want to get the problem addressed relatively soon. Driving with a tiny evaporative emissions system leak does not typically damage the car immediately, but it could lead to other damage down the road if you don’t fix it.
If you continue driving with an unresolved P0456 code, the check engine light will stay on. If you ignore it, you may not notice when a new engine problem occurs.
Lastly, fuel vapours are not only harmful to the environment, but possibly to you as well. If you are exposed to gasoline vapours for a long time, it is possible for vapours from gasoline to cause headaches, breathing trouble, and other health issues.
What Causes the P0456 Code?
Usually, this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivably cause this code as well, or if the cap wasn’t properly tightened. Any of the following could also be the cause:
- A damaged or loose gas cap
- A disconnected EVAP hose
- Faulty purge volume control
- Faulty canister vent
- EVAP canister leak
- Leaking fuel tank
- The purge solenoid valve is stuck or won’t close properly.
- Loose fuel tank hoses
- The fuel filler cap fails to close.
- Incorrect fuel filler cap applied.
Symptoms of the P0456 Error Code
The P0456 code often has associated symptoms that usually differ depending on the severity of the problem. Here are some of the most common symptoms.
- Illuminated Check Engine Light: The most apparent symptom is an illuminated “Check Engine” light on the dashboard.
- Fuel Smell: Strong odors of fuel around the vehicle, especially near the back of the car by the fuel tank, could indicate a leak in the EVAP System.
- Decreased Fuel Efficiency: Although rare, a malfunctioning EVAP system may result in a slight drop in fuel efficiency.
- Failed Emissions Testing: Vehicles with P0456 codes typically fail emissions testing because of increased hydrocarbon emissions.
- No Real Difference in Performance: We typically do not see an indication of a problem that limits the drivability of the vehicle or has any performance issues with the car.
Diagnosing the P0456 Error Code
To properly diagnose and fix a P0456 code, use the following steps:
- Check for other codes: Check with your diagnostics scanner whether there are any additional trouble codes that could relate to the P0456 code. Additional codes could help further diagnosis the issue. Codes P0440–P0455 all indicate a problem relating to the EVAP system, although they may represent different issues related to the system or could be even closely related.
- Clear and road test the code: Use the OBD reader to erase the trouble codes and then drive the car for a day or two (about 20-30 miles of normal driving test). After the drive, rescan the car to see if the problem has reappeared. If not, it could have just been a fluke, otherwise if the problem comes back you do have yourself a problem.
- Gas cap: Make sure the gas cap is on tight and make sure it is not damaged in any way. If the O-ring on the gas cap is damaged than replace the cap. A loose/missing/damaged gas cap is the most common cause of a P0456, so make sure you check this.
- Smoke Test: A smoke test is a great way to locate small EVAP leaks. The smoke machine fills the entire system with smoke and you can easily see where the smoke exits at. Smoke tests are very effective at locating small leaks.
- Inspect the EVAP hoses: Inspect the hoses for holes, cracks, and/or disconnected hoses. If needed replace hoses, etc.
- Inspect the Fuel Tank: Visually inspect the fuel tank for any broken items in or around it, etc., repair or replace if necessary. Cracked tanks will leak fuel vapors out and could create a fire.
- Leak Detection Pump: Finally check if the evaporative emission systems leak detection pump is working properly. A malfunctioning pump may signal a leak when there may not actually be one by replacing the pump you have a device that will accurately register the presence of leaks.
How to Fix the P0456 Code
If you’re confident in your repair skills, you may want to turn the P0456 code repair into a DIY repair, but a leak in the evaporative emission system is one of the hardest repairs to locate and repair, so here are things you can do.
Replace the Gas Cap
If you have an issue with the gas cap, try just tightening it and see if that resolves the code. If it does, you should be able to drive your vehicle indefinitely without the code reappearing.
If you see any damage to the gas cap, replace it before moving further. It’s an inexpensive part that is easy to repair and the quickest repair if it works.
Replace the Hoses
Oftentimes, code P0456 can be set from cracked or disconnected EVAP hoses around the engine air box. If you see any damage to the hoses, please replace them!
Purge Volume Control Valve Repair
The purge volume control valve could be sticky as well, and that could be a source of a leak in your emission system. To check, remove the hoses and blow air through them while they are not powered.
If the air passes through and there is no power, that means they are not the source of the leak. If air doesn’t pass through, that may indicate a leak, and the part may need to be replaced or cleaned.
Check the Charcoal Canister Vent Control Valve
Similar to the earlier part, the charcoal canister vent control valve could also fail to close properly, creating a leak through it. It’s possible the internal solenoid had failed, numbing the part’s functionality. When checking for possible leaks in the valve, you’ll want to check for air from the hoses and the part itself.
To check for leaks, unplug the connector/hose and can attempt to blow air through the opening while powered off. Air passing is functioning properly.
With one side of the electrical connector powered or a fuse in between and attached to a ground, attempt to blow air through the other side away from the harness. With power applied, there should not be air passing through. If there was air, then that circuit most likely isn’t a leak location either.
Run a Smoke Test
If you are having a hard time locating the evaporative emission system leak, running a smoke test can be beneficial. You can either buy a smoke tester to run a test or consider taking your vehicle into a shop to run a smoke test to help identify the location of the leak.
If the location of the leak is too difficult to identify and repair, Prudence may indicate having a professional shop diagnose the leak. Solutions for the P0456 code on a Ford vehicle might not be the same as those on a Dodge, and these fixes may work for many sizes but may not work for all.
Ways to prevent the P0456 code
While you cannot avoid all the causes of the P0456 code, performing proper maintenance can reduce the likelihood of dealing with issues relating to this code. Here are some ways to help you prevent the P0456 code from appearing:
- Regularly check the gas cap: Ensure there is no damage to the gas cap and make sure to securely tighten the gas cap every time after refilling the gas tank.
- Maintain and Have the EVAP system checked: During your regular vehicle checkups, make sure your mechanic checks the EVAP system so you can address a possible problem before it happens.
- Use quality fuel: Some low-quality fuels may have impurities that can clog or damage some of the components of the EVAP system.
- Do not overfill the fuel tank: Overfilling the tank can damage the EVAP system because it can allow liquid fuel into components designed for vapor only.
What is the cost of fixing a P0456 code?
A minor leak could set you back anything between $200 and $300. A $100 diagnostic fee is standard in many shops, with an additional $100 if the leak is difficult to find or if the components are hard to reach.
In many cases, the repair is a new hose, a rubber gasket, or a new fuel cap, which are inexpensive. However, it’ll likely be more expensive if the leak stems from the filler neck or the gas tank. In this case, you could expect to pay between $500 and $600.
For error code P0456, one or more of the following repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to repair.
- Gas Cap – $20-$60
- Evap Purge Volume Control Valve – $150-$200
- Charcoal Canister Vent Control Valve – $150-$200
- Replacement Evap Line – $50-$100
- Charcoal Canister – $200-$600
- Replace Fuel tank – $450 to $3,000.
Not all manufacturers use the P0456 code, so it isn’t as common as you may think. Yet, even when it does come on, it’s not normally indicative of a major problem. In most cases, you can simply tighten up the gas cap or replace it.
Even if there’s a part that needs to be replaced, the fix isn’t typically expensive, with many fixes costing $200 or less, especially if you can do the job yourself.
Conclusion
The P0456 error code is a frequent OBD-II code that indicates a very small leak in the EVAP system. It does not directly affect vehicle performance, but if unresolved can lead to increased emissions and other long-term issues.
By knowing the causes, symptoms, and solutions in this article, vehicle owner’s can adequately fix the P0456 code. Regular maintenance and care of the EVAP system can reduce the chances of the error code appearing and keep your vehicle running well.